void main() {
  var record = ('first', 'last', a: 2, b: true);
  print(record); // 输出: (first, last, a: 2, b: true)

  print(swap((1, 2)));

  (String, int) record2 = ('first', 1);
}

// 记录类型
(int, int) swap((int, int) record) {
  var (a, b) = record;
  return (b, a);
}
